Showing papers on "Inertial reference unit published in 2017"

Initial Alignment for a Doppler Velocity Log-Aided Strapdown Inertial Navigation System With Limited Information

Abstract: This paper proposes an ingenious alignment scheme for a Doppler velocity log-aided strapdown inertial navigation system with only the initial velocity and position information. The proposed scheme decomposes the task into two tightly coupled subproblems. First, an optimization-based coarse alignment (OBCA) method is developed to derive the constant attitude at the very start of the alignment. During the OBCA process, the required velocity and position are all approximated using their initial values. Second, a nonlinear-filtering-based fine alignment (NFFA) is developed to refine the attitude and calculate the real-time velocity and position. In an NFFA, the standard inertial navigation equations are used directly as the process model, which, therefore, can track the vehicle maneuverability during the alignment period. The NFFA is carried out again from the very start, initialized with the roughly known attitude by OBCA and the known initial velocity and position information. This scheme necessitates the recording of the sensor data during the OBCA. The experimental results show that the proposed method can not only align the attitude to high precision within very short time, but also determine the velocity and position with satisfied accuracy.

A Wearable Inertial Pedestrian Navigation System With Quaternion-Based Extended Kalman Filter for Pedestrian Localization

Abstract: This paper presents a wearable inertial pedestrian navigation system and its associated pedestrian trajectory reconstruction algorithm for reconstructing pedestrian walking trajectories in indoor and outdoor environments. The proposed wearable inertial pedestrian navigation system is constructed by integrating a triaxial accelerometer, a triaxial gyroscope, a triaxial magnetometer, a microcontroller, and a Bluetooth wireless transmission module. Users wear the system on foot while walking in indoor and outdoor environments at normal speed without any external positioning techniques. During walking movement, the measured inertial signals generated from walking movements are transmitted to a computer via the wireless module. Based on the foot-mounted inertial pedestrian navigation system, a pedestrian trajectory reconstruction algorithm composed of the procedures of inertial signal acquisition, signal preprocessing, trajectory reconstruction, and trajectory height estimation has been developed to reconstruct floor walking and stair climbing trajectories. In order to minimize the cumulative error of the inertial signals, we have utilized a sensor fusion technique based on a double-stage quaternion-based extended Kalman filter to fuse acceleration, angular velocity, and magnetic signals. Experimental results have successfully validated the effectiveness of the proposed wearable inertial pedestrian navigation system and its associated pedestrian trajectory reconstruction algorithm.

Development of a Wearable Device for Motion Capturing Based on Magnetic and Inertial Measurement Units

Abstract: This paper presents a novel wearable device for gesture capturing based on inertial and magnetic measurement units that are made up of micromachined gyroscopes, accelerometers, and magnetometers. The low-cost inertial and magnetic measurement unit is compact and small enough to wear and there are altogether thirty-six units integrated in the device. The device is composed of two symmetric parts, and either the right part or the left one contains eighteen units covering all the segments of the arm, palm, and fingers. The offline calibration and online calibration are proposed to improve the accuracy of sensors. Multiple quaternion-based extended Kalman filters are designed to estimate the absolute orientations, and kinematic models of the arm-hand are considered to determine the relative orientations. Furthermore, position algorithm is deduced to compute the positions of corresponding joint. Finally, several experiments are implemented to verify the effectiveness of the proposed wearable device.

Hardware and software architecture of multi mems sensor inertial module

Abstract: The paper describes the hardware and software architecture of the developed multi MEMS sensor prototype module, consisting of ARM Cortex M4 STM32F446 microcontroller unit, five 9-axis inertial measurement units MPU9255 (3D accelerometer, 3D gyroscope, 3D magnetometer and temperature sensor) and a BMP280 barometer. The module is also equipped with WiFi wireless interface (Espressif ESP8266 chip). The module is constructed in the form of a truncated pyramid. Inertial sensors are mounted on a special basement at different angles to each other to eliminate hardware sensors drifts and to provide the capability for self-calibration. The module fuses information obtained from all types of inertial sensors (acceleration, rotation rate, magnetic field and air pressure) in order to calculate orientation and trajectory. It might be used as an Inertial Measurement Unit, Vertical Reference Unit or Attitude and Heading Reference System.

Human motion tracking based on complementary Kalman filter

Abstract: Miniaturized Inertial Measurement Unit (IMU) has been widely used in many motion capturing applications In order to overcome stability and noise problems of IMU, a lot of efforts have been made to develop appropriate data fusion method to obtain reliable orientation estimation from IMU data This article presents a method which models the errors of orientation, gyroscope bias and magnetic disturbance, and compensate the errors of state variables with complementary Kalman filter in a body motion capture system Experimental results have shown that the proposed method significantly reduces the accumulative orientation estimation errors

Expanded calibration of the MEMS inertial sensors

Abstract: A new calibration method for Inertial Measurement Unit (IMU) of strapdown inertial technology was presented. IMU has been composed of MEMS accelerometers, gyroscopes and a circuit of signal processing. Normally, a rate transfer test and multi-position tests are used for IMU calibration. The new calibration method is based on whole angle rotation or finite rotation. In fact it suggests to turn over IMU around three axes simultaneously. In order to solve the equation of calibration, it is necessary to provide an equality of a rank of basic matrix into degree of basic matrix. Normally MEMS gyroscopes have got g- and g2-drifts. It is proposed a way of finding such drifts. The results of simulated IMU data presented to demonstrate the performance of the new calibration method.

Inertial system for gravity difference measurement

Abstract: The inertial system for gravity difference measurement uses COTS nano accelerometer and a strapdown Global Navigation Satellite System (GNSS)-aided inertial measurement unit (IMU) The former has low measurement noise density, while the latter is used to analytically stabilize the platform Stochastic modeling of the gravity anomaly is utilized (as opposed to the deterministic modeling of causes and effects) to simplify the algorithm The algorithm aims at finding relative changes between points, as opposed to absolute values at the points, which allows for high relative precision required in many applications

Improvement on the Pitch and Roll Output of Rotation Inertial Navigation System

Abstract: Experiments show that the rotation inertial navigation system has better position and velocity accuracy compared with the nonrotation inertial navigation system. But the pitch and roll output accuracy of the former is worse. This paper proves that the vortex motion of inertial measurement unit, an unexpected angular motion along other two directions perpendicular to the rotation direction, is the key cause of attitude accuracy loss. Detailed studies are done on vortex motion and an improved algorithm of horizon attitude based on gyro data analysis and Fourier fitting is proposed. Experiments show that the proposed attitude compensation method can improve pitch and roll output accuracy from $60^{\prime \prime }$ less than $10^{\prime \prime }$ .

A novel method of calibrating a MEMS inertial reference unit on a turntable under limited working conditions

Abstract: Micro-electro-mechanical systems (MEMS) inertial measurement devices tend to be widely used in inertial navigation systems and have quickly emerged on the market due to their characteristics of low cost, high reliability and small size. Calibration is the most effective way to remove the deterministic error of an inertial reference unit (IRU), which in this paper consists of three orthogonally mounted MEMS gyros. However, common testing methods in the lab cannot predict the corresponding errors precisely when the turntable's working condition is restricted. In this paper, the turntable can only provide a relatively small rotation angle. Moreover, the errors must be compensated exactly because of the great effect caused by the high angular velocity of the craft. To deal with this question, a new method is proposed to evaluate the MEMS IRU's performance. In the calibration procedure, a one-axis table that can rotate a limited angle in the form of a sine function is utilized to provide the MEMS IRU's angular velocity. A new algorithm based on Fourier series is designed to calculate the misalignment and scale factor errors. The proposed method is tested in a set of experiments, and the calibration results are compared to a traditional calibration method performed under normal working conditions to verify their correctness. In addition, a verification test in the given rotation speed is implemented for further demonstration.

Data processing algorithms for MEMS based multi-component inertial measurement unit for indoor navigation

Abstract: The development of lightweight MEMS sensors makes it possible to use inertial navigation for restoration of pedestrian trajectory. The main drawback of the current generation of MEMS sensors is their high level of noise and the bias instability due to incomplete factory calibration. One way to solve this problem is to create a multi-component Inertial Measurement Unit. This paper describes data processing algorithms for MEMS based multi-component Inertial Measurement Unit for indoor navigation. The module is constructed in the form of a truncated pyramid with five inertial sensors mounted on its planes at different angles relative to each other. The data from each sensor is fused to increase the accuracy of trajectory estimation.

Robust inertial frame-based alignment of fiber-optic gyro strapdown inertial navigation systems using a generalized proportional-integral-derivative filter

Abstract: Abstract. Initial alignment is one of the most prominent and vital issues in fiber-optic gyro strapdown inertial navigation systems (SINS). In most research, the standard Kalman filter (KF) and its various versions have been used to accomplish the initial alignment of SINSs. A robust alignment approach is presented based on a generalized proportional–integral–derivative filter. The proposed inertial frame-based alignment approach outperforms the standard KF-based alignment methods and achieves a robust and accurate solution for marine fiber-optic SISN alignment. Experimental results also verify the prominent performance of the presented approach compared to the conventional standard KF-based alignment method.

Research on ZUPT technology for pedestrian navigation

Abstract: When the satellite signal is blocked, the ground terminal cannot be accurately positioned because it cannot receive the satellite signal. In this case, it is necessary to study how to use other ways to achieve positioning and navigation. Inertial navigation inertial sensors to rely on sensing carrier acceleration and angular velocity, the position of the carrier can provide continuous in is not dependent on any external signal, speed and attitude, autonomous navigation carrier, and therefore can be used as a means to enhance the single satellite navigation and positioning. In this paper, we design a scheme to enhance the positioning accuracy by using the fusion of chip level MEMS inertial sensor and single satellite scanning position.

Method and system for controlling satellite from any attitude to sun pointing attitude

Abstract: The invention discloses a method for controlling a satellite from any attitude to a sun pointing attitude. The method for controlling the satellite from any attitude to the sun pointing attitude comprises the steps of measuring inertial angle increment by using an inertial reference unit; differentiating the inertial angle increment to obtain inertial angular velocity; measuring the specific direction of the satellite where the sun appears by using a 0-1 type sun sensor and carrying out sun acquisition to obtain a sun direction signal; controlling satellite attitude acquisition by using the change of the sun direction signal; and reducing an included angle between sun vector and one axis of the satellite so as to carry out sun pointing. By using the sun direction information of the 0-1 type sun sensor, the sun can be acquired; and through the change of the sun direction signal, the satellite can be controlled to point the sun to provide satellite guarantee for energy supply of the whole satellite; and beneficial effects of realizing the satellite from any attitude to the sun pointing attitude only by using the inertial reference unit and the 0-1 type sun sensor, improving the satellite attitude control accuracy and so on are achieved.

Calibration of an Inertial Measurement Unit

Abstract: A new method for the calibration of inertial measurement units of strapdown inertial technology is proposed. Such a unit consists of accelerometers, gyroscopes, and a signal processing system. The method of test turns and rotations on a rotary table is used to calibrate the inertial measurement unit. The new method involves measurement of the full angle of turn or final rotation. In fact, it is proposed to turn the inertial measurement unit around the axis of final rotation. To solve the calibration equation, it is necessary to make the rank of the matrix of the calibration equation equal to its order. The results of modeling data demonstrate the efficiency of the new calibration method

Hardware implementation of integrated navigation and inertial system

Abstract: The current paper describes an innovative navigation system based on GPS receiver and high speed 9 DoF IMU based on MEMS inertial sensors (3D linear accelerometer and 3D magnetometer and 3D gyroscope) which accomplishes the real-time read of the navigation and inertial data and write to FLASH memory. Also the system may transmit the data by Bluetooth or GPRS modem connected externally to the remote server. All systems and devices are connected to the microcontroller by independent interfaces which allows parallel read and write using interrupts which allows operating at very high speed (10 Hz for GPS receiver and 200 Hz for IMU system) to decrease significantly the inertial system errors.

Estimation of inertial/magnetic sensor orientation for human-motion-capture system

Abstract: An Adaptive Hybrid Filter (AHF) with generated information of inertial/magnetic sensor is designed for the fast divergence of gyro errors and the disturbance of noises in the Human-Motion-Capture System (HMCS). To address the challenges of the disturbance of noises in HMCS, we propose a novel scheme of filter fusion algorithm using inertial measurement unit and magnetometers. Gauss-Newton Algorithm (GNA) is used to process the accelerometer and magnetic data. The sensor fusion between attitude angle from GNA and gyroscope data are performed using the complementary filter. AHF can modify adaptively the parameter, thus enhancing the robustness. Evaluating the proposed scheme in magnetic field and sudden acceleration environments, the experimental results demonstrate that the proposed can achieve the accurate reproduction of HMCS.

Integration of Star and Inertial Sensors for Spacecraft Attitude Determination

Abstract: A new integration of the acquisition and tracking modes is proposed for the integration of a Celestial Navigation System (CNS) and a Strapdown Inertial Navigation System (SINS). After the integration converges in the acquisition mode, it switches to the tracking mode. In the tracking mode, star pattern recognition is unnecessary and the integration is implemented in a cascaded filter scheme. A pre-filter is designed for each identified star and the output of the pre-filter is fused with the attitude of the SINS in the cascaded navigation filter. Both the pre-filter and the navigation filter are designed in detail. The measurements of the pre-filter are the positions on the image plane of one identified star. Both the starlight direction and its error are estimated in the pre-filter. The estimated starlight directions of all identified stars are the measurements of the navigation filter. The simulation results show that both the reliability and accuracy of the integration are improved and the integration is effective when only one star is identified in a period.

Calibrating Inertial Sensors Using an Image

Abstract: A method is provided for calibrating an inertial sensing unit of a device utilizing a vision sensing unit integral to the device. The method includes receiving inertial sensing input data from the inertial sensing unit, receiving vision sensing input data from the vision unit, and determining when the received vision sensing input data represents a predetermined input state of the vision sensing unit. The method includes estimating an error value in the inertial sensing input data received from the inertial sensing unit based on the received vision sensing input data upon determination that the received vision sensing input data represents the predetermined vision sensing input state. The method further includes adjusting first subsequent received inertial sensing input data from the inertial sensing unit based on the estimated error value, thereby calibrating the inertial sensing unit.

The error online calibration technique of integrated navigation system with distributed multi inertial node

Abstract: Distributed network technology is a new application of inertial navigation technology. A distributed multi-source navigation system, constituted of a distributed inertial navigation system and a multi-senor configuration, can greatly enhance aircraft survival and reliability. Aiming to design a distributed inertial/star sensor/satellite integrated navigation system, this paper studies the structure of the distributed inertial sensor. According to the main node of the inertial measurement unit (IMU), this paper presents an error online calibration method for the integrated navigation system. It establishes the measurement error model of inertial sensor error, including installation error, scale factor error, and random constant error, and designs a 27-dimensional Kalman filter model, including gyroscope and accelerometer error status information. Furthermore, it designs a model of the distributed error calibration for IMU at sub-node. The simulation results show that the proposed online calibration model can effectively calculate the error parameters of the distributed IMU system, effectively enhancing the performance of the integrated navigation system.

A self-calibration method in single-axis rotational inertial navigation system with rotating mechanism

Abstract: Rotary inertial navigation modulation mechanism can greatly improve the inertial navigation system (INS) accuracy through the rotation. Based on the single-axis rotational inertial navigation system (RINS), a self-calibration method is put forward. The whole system is applied with the rotation modulation technique so that whole inertial measurement unit (IMU) of system can rotate around the motor shaft without any external input. In the process of modulation, some important errors can be decoupled. Coupled with the initial position information and attitude information of the system as the reference, the velocity errors and attitude errors in the rotation are used as measurement to perform Kalman filtering to estimate part of important errors of the system after which the errors can be compensated into the system. The simulation results show that the method can complete the self-calibration of the single-axis RINS in 15 minutes and estimate gyro drifts of three-axis, the installation error angle of the IMU and the scale factor error of the gyro on z-axis. The calibration accuracy of optic gyro drifts could be about 0.003°/h (1σ) as well as the scale factor error could be about 1 parts per million (1σ). The errors estimate reaches the system requirements which can effectively improve the longtime navigation accuracy of the vehicle or the boat.

Eddy-Current Sensing Principle in Inertial Sensors

Abstract: The eddy-current displacement sensing principle is, to the best of our knowledge, not yet used in inertial sensors. The main reasons for this are the important performance limitations of the existing eddy-current sensor solutions, such as low sensitivity, poor stability, high-power consumption, and bulkiness. Our novel high-frequency eddy-current displacement sensor (ECDS), however, has significantly improved performance with respect to these limitations and allows the use of planar, stable coils, making it a viable candidate for the use in inertial sensors. An implementation example of an ECDS-based inertial sensor with a bandwidth of 370 Hz and a noise floor of $13\,\mu {\text{g}/ \surd \text{Hz}}$ is proposed. Although not yet competitive with state-of-the-art inertial sensors, it performs better than other types of inductive accelerometers and offers the inherent advantages of ECDSs, such as insensitivity to the environment.

Calibration of in-run drifts of strapdown inertial navigation system with uniaxial modulation rotation of measurement unit

Abstract: Errors of a strapdown inertial navigation system (INS) based on navigation grade fiber-optic gyros (FOG) are studied, with the INS measurement unit performing modulation rotation about the axis orthogonal to the vehicle deck. The main focus is made on the problem of reducing the time of gyro in-run drifts calibration, using the GNSS data when the INS is turned on. In addition to velocity and position measurements taken by the GNSS, phase measurements from antennas spaced on a certain baseline are included.

A review on measuring cervical range of motion using an inertial measurement unit

Abstract: Objectives: The purpose of this study was to review the article using an IMU(Inertial Measurement Unit) for measuring the cervical range of motion and to evaluate the feasibility of using an IMU for measuring the cervical range of motion. Method: Scopus was used to search for the articles relating to the inclusion criteria. Which is measuring the cervical range of motion using an IMU. A total of 15 articles were selected through discussion. Degree and the reliability of the cervical range of motion and the validity of the data within the articles were extracted. Results: The measurement of the cervical range of motion using an IMU were 92.25o to 138.2 o , 122.4o to 154.9o, 73.75o to 93.1o on the sagittal plane, transverse plane, and coronal plane respectively. 38 of the 43 values showed good reliability. They were larger than 0.75. 5 of the 43 values showed reliability less than 0.75. They were measured by smart phone. 16 of the 21 values showed good validity. The remaining 5 were measured by smart phone. The lower reliability and validity of smart phone were related to the protocol. The IMU can measure the coupling motion and may be used in various situations. Conclusion: The IMU may become a gold standard for measuring the cervical range of motion. The IMU measured not only the cervical range of motion but also the coupling motion. Furthermore, IMU may be used in various situations. Therefore, IMU must be considered a valuable measurement device.

Human Motion Characterization Using Wireless Inertial Sensors

Abstract: In this paper the developed wireless IMU (inertial measurement unit) system for human motion characterisation has been described. The experimental layout, test modes and protocols were defined. The experiments for the knee joint characterisation during walking on an inclined treadmill were presented. The human knee joint’s characterisation with the usage of IMU sensors communicating with an Arduino board connected to a computer, was presented by plots and numerical data from experiments.